Wednesday, May 23, 2007

Platelet rich plasma in a paper published in the Archives of Facial Plastic Surgery (Hom et al May/June 2007) has been shown to improve closure rates of skin wounds. Specifically, at day 17 after a skin punch wound, 81% of PRP treated wounds were closed versus 57% of controls. The closure velocities were also faster. (p = 0.001).

This is clear evidence that PRP enhances wound healing. In orthopedics and a variety of other specialties, PRP should be strongly considered when doing procedures that have a potentially high wound complication rate such as achilles tendon repair.

The rate of platelet rich plasma publications has also risen dramatically. This indicates more interest in PRP and now more evidence to support its use.

Sunday, May 13, 2007

It is clear that PRP induces increased proliferation in a variety of cell types including fibroblasts and mesenchymal stem cells. This recently published paper discusses how PRP may inhibit macrophage proliferation at least initially. This has broad implications for wound and tissue healing. Further research into these findings should be available soon.

Healing injured tissue in the body is a complex process which consists of four distinct phases: hemostasis, inflammation, proliferation, and remodeling. Each of these phases is coordinated by growth factor release and cell to cell interactions. Platelet rich plasma (PRP) is a fraction of plasma that has been isolated and used to enhance regeneration in bone and soft tissues. The healing potential of PRP has been attributed to the release of multiple growth factors from the highly concentrated platelets. While there is strong evidence of the pro-stimulatory effect on the cellular proliferation phase of healing, there is little evidence of the effects of PRP on the inflammatory phase of healing. In this study we investigate the effect that PRP has on macrophage cells in culture and the implications this has on the healing process. We investigate specifically the effects of the separate cellular components of PRP, as a whole and individually, on cell proliferation in human macrophage cells in culture. In contrast to the pro-stimulatory effect that PRP has on cells such as osteoblasts, fibroblasts, and tendon cells; our results show a suppression of macrophages by PRP as early as 24 hours after treatment. This suppression was statistically significant (p=0.002) and continued to be significant for the duration of the study. The cell viability results of PRP compared to platelet poor plasma (PPP) and individual components of PRP showed that PRP resulted in a steady increase in viability following the initial insult to the macrophage cells, while the viability of other treatment groups seemed to plateau.

Monday, May 07, 2007

pH is a measure of the relative acidity of a solution. Physiologic pH is around 7.4. Most commerical PRP preparation machines produce PRP in the zone of 6.9-7.0 in terms of pH. Why is this important? Because the growth factors within PRP work differently at different pHs. Also, the amount of initial pain from an application of acidic PRP is much greater than neutral PRP. Here is a recently published abstract that supports the use of neutral or alkaline PRP. Clearly, more work needs to done in this area. For now, however, converting acidic PRP to neutral PRP appears to have significant value.

Activated platelets release a multifaceted blend of growth factors that has stimulatory effects on mesenchymal cells, both in vitro and in vivo, which imply beneficial effects on wound repair and tissue regeneration. Previous studies on fibroblast cultures have revealed that more potent growth factors, with respect to cell proliferation, are released in acidic preparations of lysed platelet concentrates in comparison with neutral and alkaline preparations. The current study was intended to investigate the influence of pH on lysed platelet concentrates with respect to release of growth factors, cell proliferation and alkaline phosphatase (ALP) activity in human osteoblast-like cells (hFOB 1.19). Cell proliferation was assessed with the MTT kit, ALP activity by conventional enzymatic reaction kinetics and growth factors platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) by enzyme-linked immunosorbent assays. Osteoblast-like cells were stimulated with lysed platelet concentrates preincubated at pH 4.4, 5.4, 7.4, and 7.6. A 3-13-fold increase of cell proliferation was found in comparison with controls and the most evident increase was observed with platelets activated at pH 5.4. The highest ALP activity was observed in preparations at pH 7.6. Platelets incubated in an acidic environment (pH 5.4) induced a higher proliferation compared with preincubation at neutral or alkaline pH and the level of PDGF was also found to be higher in acidic preincubations. The level of TGF-beta was, in contrast, lowest at pH 4.4. We suggest, based on these experimental findings, that acidic milieu influence platelets to release growth factors more potent to stimulate osteoblast proliferation than neutral and alkaline platelet preparations. Lysed platelet concentrates prepared at an alkaline pH might release additional components with stimulating effects resulting in other features than cell proliferation. This is the first report, to our knowledge, about a pH dependent stimulatory effect of lysed platelet concentrates on human osteoblast-like cell proliferation. Lysed platelet concentrates, preincubated in acidic or alkaline buffers, may benefit fracture healing, implant fixation and might also be advantageous in the treatment of wounds with platelet constituents; however, this has to be investigated in extended experimental and clinical settings.